Method for producing a coloured mineral wool product comprising the same colour coating

ABSTRACT

The invention relates to a method for producing a mineral fibre board which comprises a coloured pigment and whose at least one surface is provided with a non-woven coating made of a substantially black material. The inventive method consists in inserting the coating into a board production device, wherein said coating is embodied in the form of a fabric, which is based on a polyester with appropriate weight per unit square, not precoloured and not impregnated or provided with an additional adhesive agent introduced therein for adhering to fibre pads. A coloured mineral wool product provided with the same colour coating produced by the inventive method is also disclosed.

The invention relates to the field of boards based on mineral fibers, particularly glass fibers, comprising a color surfacing. It applies more particularly to the production of acoustic and/or thermal insulation products, such as, for example, rolled boards for acoustic insulation, having high quality and low thickness dyed in the mass and coated with a coating having an identical color, for example black.

Insulating boards sold today consist of a pad or felt of mineral fibers, such as glass fibers joined by an organic binder. A layer of a coating is commonly bonded to the visible side of the felt, said coating performing several functions. For example, ornamental effects may be desired to impart a finished or at least a uniform appearance to the finished product. The coating may also have a role of improving the mechanical strength of the felt.

The choice of a coating may further be guided by the search for better board user convenience, particularly during installation. It is in fact well known that the handling of glass fiber based products can cause harm or irritation to the handler's skin or eyes, and it is therefore advantageous for the fibers to be maintained confined in the felt.

Among the coatings commonly used today, mention can be made of polyvinyl chloride films, glass fiber fabrics which may optionally be painted, kraft type papers, and aluminum films on kraft paper.

In certain versions of these boards, called “comfort” versions, an attempt is made to preserve a generally uniform aesthetics of the product and, above all, to improve the touch of these surface coatings, in order to further improve the user's comfort.

Besides the fact that these coatings must be suitable for obtaining an end product that is easy and comfortable to use and performs all or part of the abovementioned functions, they must also be able to sufficiently withstand a local stress such as a pressure applied with the finger, and have good fire resistance properties.

To meet this set of requirements, a number of nonwoven materials can be proposed for coating a mineral wool felt: polypropylenes and low basis weight glass fiber fabrics. Nonwoven polypropylenes must be applied to the mineral wool pad after any heat treatment step, particularly oven drying, because they cannot withstand the treatment temperatures. The glass fabrics used for the time being procure a feel that is less pleasant to the touch, and are not always sufficiently able to withstand a local pressure.

Furthermore, in certain uses of glass fiber boards such as rolled boards, a colored pigment is sometimes blended with the mineral wool during its formation, as illustrated below. A colored board can thereby be obtained, whereof the color is immediately associated by the user with a clearly defined function. Such a color code is, for example, illustrated by the Soniroll® reference product from Saint Gobain Isover and available in the form of semi-rigid rolled boards of glass wool dyed in the mass by a black carbon pigment and coated with a prepainted black glass fiber fabric. The black color is identified by the consumer with the use of the product as acoustic insulation for walls and ceilings. The glass fabric is relatively dense (high basis weight of about 60 g/m²) and also presents problems of flaking upon unwinding.

A simple method for producing a mineral fiber board has now been discovered, said board comprising a colored pigment and at least one of its sides being coated with a nonwoven coating of an essentially black material. Said method is characterized in that the coating of the form of a polyester based fabric having an appropriate basis weight is introduced into the installation for producing the boards without precoloring treatment and without impregnation or introduction of additional adhesive for its adhesion to the fiber pad.

More precisely, the invention relates to a method for producing a mineral wool product, such as glass wool, said wool being dyed and comprising a coating of the same color, in which the mineral wool is gathered to form a fiber pad on conveyor means after spraying by a binder curable under the effect of heat and after blending with colored pigments, then introduced into a crosslinking chamber, said method being characterized in that the coating is a polyester fabric and in that said polyester fabric is contacted with the pad before introduction into the chamber, without the addition of dye and without impregnation or introduction of additional adhesive for its adhesion to the fiber pad.

Preferably, according to said production method, the conveyor means are permeable to gases and are mounted on means for aspirating said gases.

According to a first embodiment, the polyester fabric is introduced on the conveyor means before placing the fibers on said conveyor means.

According to a second embodiment, the polyester fabric is introduced above or below the fiber pad, immediately before the introduction of said pad into the crosslinking chamber.

The invention also relates to the colored mineral wool product comprising a coating of the same color, such as a rolled surfaced board, obtained by a method as previously described.

Other details, features or advantages are illustrated by the nonlimiting example that follows, in which one embodiment of the invention is described, with reference to the figure appended hereto, which schematically shows a production line for insulating boards based on glass wool.

Such a line comprises a fiberizing unit 1 perfectly known per se, for example according to the method of fiberizing by the internal centrifugal process whereof exemplary embodiments are described in applications EP 0 406 107 or EP 0 461 995. The fiberizing unit comprises a hood (not shown in FIG. 1) surmounted by one or more centrifuges 2, 2′. Each centrifuge comprises a basket (not shown in FIG. 1) for recovering molten glass and a plate shaped member 23 whereof the peripheral wall is provided with a large number of orifices. In operation, the molten glass, conveyed in a stream 3 from a melting furnace (not shown) and first recovered in the centrifuge basket, escapes through the orifices of the plate 23 in the form of a multitude of rotated filaments. The centrifuge 2 is moreover surrounded by an annular burner 4 which creates, at the periphery of the centrifuge wall, a gas stream at high speed and sufficiently high temperature to draw out the glass filaments in fibers in the form of a torus 17. The fiberizing by this method is complete and produces 100% of useful fibers. The method also guarantees long and flexible fibers.

Heating means 5, for example of the induction coil type, serve to maintain the glass and the centrifuge at the proper temperature. The torus 17 is closed by a gaseous air stream introduced under pressure, illustrated by the arrows 6. The torus 17 is surrounded by a device for spraying sizing containing the binder in aqueous solution, whereof a single element 7 is shown in FIG. 1. A device 21 is used for introducing, for example, a colored pigment into the core of the mass of newly formed glass fibers, at the same time and substantially at the same height. Without extending beyond the framework of the invention, the same device could be used for introducing the binder and pigment, for example, premixed.

The bottom of the fiberizing hood consists of a fiber receiving device comprising a conveyor incorporating an endless belt 9 permeable to gases and water, under which suction boxes 10 are placed for sucking out gases such as air, fumes and surplus aqueous compositions produced by the fiberizing process previously described. A pad 11 of glass wool fibers intimately mixed with the pigment and the binder is thereby formed on the conveyor belt 9. The pad 11 is led by the conveyor to a crosslinking chamber 12. This chamber 12 commonly consists of a closed chamber comprising a series of compartments fed by burners with hot air circulated by fans (not shown in FIG. 1). The chamber is traversed by two complementary transport and sizing conveyors 13, 14. These conveyors 13, 14 are, for example, rotated by motors placed in the pits 15, 16, and consisting, according to the teaching of patent FR 2 394 041, of a succession of interhinged perforated rigid vanes.

While ensuring the passage of the hot gases favoring the rapid setting of the binder, the conveyors 13, 14 compress the pad to impart the desired thickness thereto. By way of example, a rolled board is typically between 10 and 150 mm thick, preferably between 20 and 100 mm thick, the density of the glass fiber layer being, for example, between 10 and 100 kg/m³, preferably between 20 and 80 kg/m³.

According to the invention, a support is introduced on the belts 9, upstream of the crosslinking of the fiber pad in chamber 12, said support consisting of a polyester fabric which constitutes the surface coating of the final product obtained. In the example shown in FIG. 1, the introduction takes place upstream of the placing of the fiber pad on the conveyor. The polyester fabric 18 is conventionally uncoiled from a roller 19 and pressed against the upper part of the conveyor belt 9 by the action of a tension roller 20. The polyester fabric serving for the final coating is thereby simply and cheaply placed between the pad of newly formed fibers 11 and the suction boxes 10. The suction phase carried out by the boxes 10 conventionally serves to lower the moisture content of the fibers and of the binder but also, according to the invention, a good adhesion of the fibers distributed on the lower part of the felt with the polyester fabric, without using additional means. In particular, under the effect of the suction, the binder, commonly used for the cohesion between the fibers, also impregnates the polyester fabric 18. In consequence, no further addition of adhesive is necessary, thereby permitting substantial savings in the total cost of the method and, above all, without degrading, indeed improving, the fire resistance of the final product, for example in the sense of Euroclasses according to standard NF EN 13501. In particular, the impregnation is improved by the fact that the polyester fabric, first confined on the conveyor 9, is then pressed against the fibers by the suction effect 10 and then finally compressed against them by the conveyor belt rollers 14 before and during the curing in the chamber 12.

The curing causes the evaporation of the water, the crosslinking of the binder between the fibers of the pad, and also a strong adhesion between the impregnated polyester fabric 18 and the bonded and sized pad 22. Obviously, a known or tested polyester fabric is selected according to the invention for withstanding, without substantial degradation of its structure and/or of its dimensions, the temperatures commonly used for said crosslinking, during a period at least equal to and preferably longer than the time of passage of the fabric in the chamber 12. By way of example, these temperatures are typically between 100 and 250° C., preferably between 150 and 220° C. The polyester fabric used according to the invention may furthermore have undergone a pretreatment for improving its fire resistance and may thereby, for example, comprise fillers known for a fireproofing function, such as certain oxides.

It should also be pointed out that according to the invention, a polyester fabric is used whereof the basis weight permits the passage of the gases, so that the air suction phase can be carried out without causing additional or excessive pressure drops across the suction boxes 10 during the accumulation of the fiber mass. The expression excessive disturbances means here disturbances liable to hamper the satisfactory progress of the method or the optimal organization of the fibers in the felt.

Although it is not restricted to this interval, the basis weight of the polyester fabrics used according to the invention is thus typically between about 10 and 50 g/m², preferably between 15 and 30 g/m², and highly preferably between about 15 and 20 g/m².

One of the advantages of using a polyester fabric is hence to offer a possibility of introducing the fabric far upstream in the board production method. Such a method appears to be very difficult to implement without strongly disturbing its operation, if a conventionally used glass fiber fabric is introduced at this stage, due to the excessive suction pressure drop caused by this introduction.

Finally, the method as described serves advantageously, simply and economically, to directly use a polyester fabric, that is one that has not undergone any initial coloring or dying treatment to supply the roller 19. Although it is admitted that to obtain the color dyed coating of the present Soniroll® product comprising a black glass fiber fabric or equivalent product, a step for impregnating the fabric in an inking bath is necessary, it has now been discovered that the white polyester fabric is impregnated not only with the adhesive but also with the colored pigments initially distributed by the device 21 during the fiberizing. It has also been found that this effect is particularly intense and visible if, as illustrated in FIG. 1, the polyester fabric is introduced on the conveyor belt 9 before the reception of the fibers on said conveyor, in the chronology of the production method. Without this being connected to any theory whatsoever, the intensity observed in the pigmentation of the polyester fabric, associated with a rapid diffusion of the pigment particles through the fiber pad, could result jointly from:

-   -   interactions between the binder and the pigment, the binder         being filled with pigment particles and favoring their migrating         toward the fabric and     -   the suction performed by the boxes 10 which favors the migration         of a sufficient quantity of binder to further guarantee the         proper adhesion of the fabric to the felt.

Contrary to what is found for a glass fabric, it has also been found that no problem of flaking of the coating is observed upon the unwinding of the final product when a polyester fabric of the invention is used.

For example, in the case in which the pigment consists of carbon particles for obtaining a black appearance of the final board, it has been observed that if a polyester fabric with a basis weight of 17 g/m², a weight percentage of 5% of binder and a carbon percentage of 1% in the dry extract with regard to the fiber mass is used, a majority of the surface of the polyester fabric on the finished board assumes a color substantially identical to that of the glass fiber pad constituting the core of the material. The expression majority of the surface means, in the context of the present description, at least 50% of said surface. This percentage could be 70% or even 80% without extending beyond the scope of the invention, according to the conditions used during the production method, for example, according to the suction capacity, the proportion or quantity of pigments used, the binder content of the felt, the perforation ratio of the receiving conveyor, etc.

The quantity of binder used is generally between 1 and 10 wt % of the fiber mass, preferably between 2 and 8 wt % and highly preferably between 4 and 7 wt %. The quantity of pigment used is variable and is generally compromised, for example determined by a person skilled in the art from routine experiments, between the fire resistance and color intensity of the coating desired on the finished product.

By way of example, for carbon black, good results in terms of dyeing and fire resistance according to standard NF EN 13501 have been observed when the quantity of pigment introduced corresponded to a weight percentage of said pigment in the dry extract, that is after drying, of between 0.1 and 5% of the fiber mass, preferably between 0.5 and 1.5% of the fiber mass.

The sizing used as binder is, for example, based on phenol formaldehyde resin optionally comprising urea, in aqueous solution or dispersion of a dry extract comprising between 30 and 60 wt %.

In the preceding embodiment, illustrated by FIG. 1, an embodiment has been described in which the polyester fabric is introduced into the method upstream of the placing of the glass fibers on the conveyor belt 9. However, it would not extend beyond the scope of the invention if said fabric 18 were introduced on the upper or lower side of the fiber pad immediately before its passage into the crosslinking chamber 12, for example at the level of the pad entry respectively on the conveyors 13 or 14. In this case, the fiber is impregnated and dyed essentially thanks to the compression exerted by the conveyor 13 or 14 on the fiber pad and the polyester fabric during the forming thereof. In this embodiment, the adhesion of the fabric to the pad, although decreased, nevertheless remains acceptable, and the decrease in coloring observed is offset by an improved fire resistance, owing to the lower migration of the binder toward the fabric.

FIG. 1 shows a fiber receiving and conveying system comprising an endless belt system. However, the present method can also be implemented by a system limiting the negative pressure undergone by the felt and comprising a plurality of receiving zones each corresponding to one or more fiberizing machines, each receiving zone consisting, for example, of a pair of inversely rotated drums, according to the principles illustrated by patent EP 0 406 107. 

1. A method for producing a mineral wool product, such as glass wool, said wool being dyed and comprising a coating of the same color, in which the mineral wool is gathered to form a fiber pad on conveyor means after spraying by a binder curable under the effect of heat and after blending with colored pigments, then introduced into a crosslinking chamber, said method being characterized in that the coating is a polyester fabric and in that said polyester fabric is contacted with the pad before introduction into the chamber, without the addition of dye and without impregnation or introduction of additional adhesive for its adhesion to the fiber pad.
 2. The production method as claimed in claim 1, in which the conveyor means are permeable to gases and are mounted on means for aspirating said gases.
 3. The production method as claimed in either of claims 1 and 2, in which the polyester fabric is introduced on the conveyor means before placing the fibers on said conveyor means.
 4. The production method as claimed in either of claims 1 and 2, in which the polyester fabric is introduced above or below the fiber pad, immediately before the introduction of said pad into the crosslinking chamber.
 5. The production method as claimed in one of the preceding claims, in which the basis weight of the polyester fabric is between 10 and 50 g/m², preferably between 15 and 30 g/m², and highly preferably between 15 and 20 g/m².
 6. The production method as claimed in one of the preceding claims, in which the pigment used is suitable for dyeing the pad and fabric black, for example, made from carbon particles.
 7. The production method as claimed in one of the preceding claims, in which the quantity of binder is between 1 and 10 wt % of the fiber mass, preferably between 2 and 8 wt % and highly preferably between 4 and 7 wt %.
 8. The production method as claimed in one of the preceding claims, in which the quantity of pigment introduced corresponds to a weight percentage of said pigment in the dry extract of between 0.1 and 5% of the fiber mass, preferably between 0.5 and 1.5% of the fiber mass.
 9. The production method as claimed in one of claims 2 to 8, in which the suction capacity and/or the quantity of pigments and/or the quantity of binder are selected so that at least 50% of the surface of the polyester fabric on the finished product has a substantially identical color to the glass fiber pad constituting the core of the material.
 10. A colored mineral wool product comprising a coating of the same color, such as a rolled surfaced board, obtainable by a method as claimed in one of the preceding claims. 